The present invention is directed to a method of using software for compressing graphic images in order that these graphic images may be stored in a substantially enhanced compressed mode on a computer memory. The present invention has especial use in all areas of archiving, such as banks, libraries, insurance companies, and the like, where the prodigious amount of data generated has hithertofore precluded, or made difficult, the transferrance of the physical copies to digital data for storage on a computer memory device. Presently, for example, in the banking industry, the records of al transactions, checks, and the like, are presently stored on microfiche, which is a costly and time-consuming operation, and which, also, requires considerable time in actual use when a check or a transaction is required to be located. Because current computer compression techniques are not capable of compressing data to a degree necessary for storing such prodigious amounts of information, computer-storage of these files has not been implemented to any great degree.
The technological process of the invention involves converting certain text and image file-types, which hitherto have been difficult or impossible to compress, into file-types that can be compressed using standard compression techniques. Thereafter, these compressed files may be decompressed and converted back into their original form for viewing, or converted into a special file-format.
Images are usually imported into computer programs by means of scanners and databases. These data-bases are in either TIFF (Tag Image File Format) or EPS (Encapsulated PostScript Language) format. TIFF files are usually text files stored as a 1 or 2-bit, B&W file. This is a file format frequently used for fax-transmissions and scanning-applications to store or send images as bit maps in various sizes, resolutions, or color depths. It is considered a low-quality, imaging file-type as compared to other file-types available. It's popularity and subsequent broad utilization, however, has been attributed to its versatile file-architecture, which stores information in "tagged fields." This allows application programs to use these "tags" by accepting or ignoring fields within the file, depending on the program's capabilities, and, is, therefore, easily adapted for use by standard faxing or scanning equipment. Presently, TIFF files can be compressed to a lower file size only using the patented LZW compression algorithm (after Lempel-Ziv and Welch, the inventors), as disclosed in U.S. Pat. No. 4,558,302. This compression-algorithm uses the Unix compress-command to reduce the size of files, e.g. for archival or transmission. There are several variants of Lempel-Zev compression schemes, which include LZ77, LZ78, LZSS, LZFG, LZB and LZH (after Lempel-Ziv and Haruyasu, the inventors), for example. While there are several compression-schemes available to reduce TIFF file size, the most popular include LZW, LZW with prediction, Pack Bits (RLE), CCITT (International Telegraph and Telephone consultative Committee Study Group) -Level 3, and -Level 4. In each of these processes, however, the deterioration of the subsequent decompressed file is quite noticeable, and, in certain circumstances, the compression ratios of the file-reduction is minimal as compared to the compression ratios of the present invention.
EPS file-formats are extremely high-quality image files used predominantly in the Desktop Publishing Industry. This file-type uses a combination of Post-Script commands and TIFF or PICT formats. PICT files, developed by Apple Computer in 1984, are encoded in "QUICKDRAW" commands, and can hold both object-oriented images and bit-mapped images. Due to the large amount of information relating to the image characteristics, i.e., size, resolution, brightness, color depth, etc., compression-algorithms available for this file-type are presently limited.